Disposable food containers are well known in the art. Disposable food containers include common paper plates, bowls, clam shells, trays, etc.
The art has paid considerable attention to making, molding, and deforming these food containers out of a single plane. In this latter process a blank is provided. The blank is inserted between mating platens and pressed. The periphery of the blank may have radial grooves. The radial grooves provide for accumulation of the material deformed by the platens. Exemplary art includes U.S. Pat. No. 3,033,434, issued May 8, 1962 to Carson; U.S. Pat. No. 4,026,458, issued May 31, 1977 to Morris et al., the disclosures of which are incorporated herein by reference; U.S. Pat. No. 4,606,496, issued Aug. 19, 1986 to Marx et al.; U.S. Pat. No. 4,609,140, issued Sep. 2, 1986 to van Handel et al.; U.S. Pat. No. 4,721,500, issued Jan. 26, 1988 to van Handel et al.; U.S. Pat. No. 5,230,939, issued Jul. 27, 1993 to Baum; and U.S. Pat. No. 5,326,020, issued Jul. 5, 1994 to Cheshire et al.
The blanks are typically comprised of paperboard, and more particularly a single sheet of paperboard, as illustrated in the aforementioned patents. A single sheet of paperboard is utilized due to the belief that to deform the blank out of its plane the blank must be thin and of a single ply. The paperboard, or other material used for the blank, is typically substantially homogeneous, as illustrated by U.S. Pat. No. 4,721,499 issued Jan. 26, 1988 to Marx et al. It is believed that homogeneity aids in the radially symmetric deformation of round food containers, such as plates and bowls.
However, these attempts in the art suffer from several drawbacks. As illustrated by the plethora of attempts to improve the rigidity and stability of the food containers, the prior art attempts do not provide food containers of sufficient strength. This lack of strength leads to spillage of food when the food container becomes overloaded, or, alternatively, unduly constrains the amount of foods which can be placed on the food container at a given time.
There have been several attempts in the art to improve the rigidity of such food containers. For example, food containers having a bottom wall, a side wall disposed radially outwardly of and circumjacent the bottom wall, and a rim disposed radially outwardly of and circumjacent the side wall are known in the art. Food containers with densified regions in the side wall have been attempted in the art. Likewise, containers having densified circumferentially spaced regions extending radially through annular portions of the rim are known. Such attempts in the art are alleged to provide resistance to bending throughout the entire structure. Illustrative of such attempts are U.S. Pat. Nos. 4,606,496 issued Aug. 19, 1986 to Marx et al. and U.S. Pat. No. 4,609,140 issued Sept. 2, 1986 to Van Handel et al.
But, the side walls/rims are usually angled relative to the plane of the food container. Such angles increase the section modulus of the side wall/rim and thereby structurally increase their stiffness without densification. There is clearly a need in the art to increase the rigidity of the planar portion of the food container, as this is the portion of the food container onto which food is typically deposited.
Another attempt in the art uses multi-ply laminate food containers. One such attempt uses single face corrugated materials, as illustrated by U.S. Pat. No. 5,577,989 issued Nov. 26, 1986 to Neary. Neary acknowledges the industry has not been able to create a satisfactory unitary construction by stamping corrugated paperboard of more than two plies. But Neary's construction does not selectively reinforce the planar portion of a food container.